Find blocking session in Oracle Database

 Find blocking session in Oracle Database

Query to find block in Oracle Database

set linesize 190
set pages 5000

col osuser for a20
col machine for a20
col username for a20

SELECT 
  sid,serial#,osuser,machine,username,sql_id,blocking_session "BLOCKING_SESSION",
  sid "BLOCKED_SESSION",
  serial# "BLOCKED_SERIAL#", 
  seconds_in_wait/60 "WAIT_TIME(MINUTES)"
FROM v$session
WHERE blocking_session is not NULL
ORDER BY blocking_session;

set linsize 190   

select s.sql_id,s.sql_text from v$session v, v$sql s where s.sql_id=v.sql_id and v.sid='&1';